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Paten'cedV April 13,- |880.

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JESSE H. BUNNELL, OF NEV YORK, N Y.

ELECTR- MAGNET.

SPEGIFICATION forming part of Letters Patent No. 226,485, dated April 13, 1880,

Application filed March 10, 1880.

To all whom, t may concern:

Be it known that I, JESSE H. BUNNELL, of New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Electro-Magnets for telegraphic and other purposes, which improvenients are fully set forth in the following speciiication, reference being had to the acconipanyin g drawings.

My invention relates to an improved conibination of permanent and electro magnets with a movable armature, intended more particularly for use in connection with telegraphic instruments, but which may be advantageously applied to other electro-magnetic apparatus.

The invention consists in placing permanent and electro magnets with their respective poles in contact in such manner that they will form a closed magnetic circuit, and in so arranging a movable armature in proximity to certain poles or projections situated at or near the points of contact between the permanent and electro magnets that the increment and decrement of the normally existing magnet-ism at the extremities of said projections produced by the opening and closing of an electric circuit in which the coil or coils of the electromagnet are included will act upon the armature in the ordinary manner, so as to cause a to-and-fro movement of the said armature, which may be utilized for telegraphic or other purposes.

l have found that by thus arranging the poles or projections which act upon the movable armature in connection with a closed magnetic circuit a given elfect upon the ar- (Model.)

B is a permanent magnet of hardened steel, powerfully magnetized in the usual manner, and supported in a horizontal position upon the base, as shown in the drawings, N being its north and S its south pole. The permanent magnet is preferably of the usual horseshoe form, and may be composed of a single plate of steel, as in the drawings, or of a number of thin plates laid up togetherin a wellknown manner, so as to form whatis termed a compound magnet. Pole-pieces n and s, preferably of soft iron, are firmly secured to the respective poles of the permanent magnet B, and virtually form continuations thereof. A cylindrical bar or core of soft iron having about the same area of cross-section as the polepieces n and s is placed transversely between the latter, so as form a magnetic connection between them at a point considerably within the extreme ends, poles, or projections thereof. Thus it will be understood that the transverse bar O, in connection with the pole-pieces a s and the permanent magnet B, forms a closed magnetic circuit, by reason of which little or no free magnetism or magnetic attraction is ordinarily manifested at the extreme ends of the pole-pieces a s, which face the armature D.

rlhetransverse bar or core O is surrounded by a coil of insulated wire, E, in the manner of an electro-magnet, the ends of said coil being carried to binding-screws z c for the convenient attachment of telegraphic or other conductors.

The movable armature D is constructed and arranged in the ordinary manner, being mounted upon a lever, F, pivoted at f. The movement of lthe armature toward and from the poles of the magnet is limited by the adjustable screw-stops g h. The armature is also provided with the usual adjustable retractingspring i.

Binding-screws l m may be provided for the attachment of a local circuit, asin ordinary relay-instruments.

rIhe operation of the apparatus is as follows: "When the coil or helix E is placed in an electric circuit, by attaching the conductors ofthe latter to the binding-screws z and c the balance of the closed magnetic circuit is disturbed by the inductive action of the coil E upon the core O, which produces magnetic polarity at the outer extremities of the pole-pieces a s, and

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causes the armature D to be attracted. W'hen the circuit through the coil E is broken the magnetic balance is restored and the armature D is drawn away by the spring Q7.

It is preferred to make the pole-pieces a s of soft iron, although this is not essential, as the apparatus may be so arranged as to allenT the armature to be acted upon directly by the poles ol' the permanent magnet, these latter being` connected with each other bythe bar C, so as to complete the magnetic circuit.

It is obvious that the form, ar 1angement, and proportions ofthe several parts described may be greatly Varied Without departing from the spirit ell my invention, but I generally prefer to employ substantially tlie arrangement herein shown and described.

l cla-im as my inventionl. An electro-m agnet the two poles of which are permanently attached to the respective poles of a permanent magnet in such manner that the intensity ofthe free magnetism at the extreme ends, poles, or projections ofthe said permanent magnet may be varied by the transmission oi'l an electric current through the coil surrounding the electro-magnet.

2. The con/ibination, substantially as herein described, or' a permanent magnet andan electro-magnet, with their respective poles permanently in contact in such manner as te form a closed magnetic circuit.

3. rI he combination7 substantially as herein described, of a permanent magnet, provided with soft-iron pole-pieces attached to each of its poles, a core of soft iron permanently connecting said pole-pieces with each other, and a coil or helix of Wire surroui'nlin g said conneeting-core.

4. The combination, substantially as set forth, of a permanent magnet, a core of soft iron permanently connecting` the two poles thereof with each other, a coil or helix of wire lsurrounding said core, and an armature so situated as to be moved to and fro by the increment and decrement or' magnetism in said poles when electrical pulsations are caused to traverse the coil. y

The combination, substantially as set forth, of a permanent magnet provided with soft-iron pole-pieces attached to each of its poles, a bar of soft iron permanently connecting said pole-pieces with each other, and a coil or helix of Wire so arranged as to cause an alternate increment and deerelnent or' the niagnetism in the said pole-pieces when electrical pulsations are caused to traverse said coil.

6. The method, substantially as herein set forth, of causing the movement of an armature by altering the normal distribution of magnetic force in the closed and balanced magnetic cir-y cuit ofa permanent magnet by means of a magnetizing coil or helix acting thereupon.

In Witness WhereoitA I have hereunto set my hand this 28th day or' January, A. l). 1880.

` J. Il. 'BUNNELL litnesses Wir. ARNoUX, MILLER G. EARL. 

